This invention relates to electrical connectors, and particularly to an electrical terminator device for terminating an open signal path of an electronic device. More particularly, this invention relates to a terminator for input/output interfaces of electronic digital computers.
Electronic digital computers are typically equipped with a plurality of input/output interface ports. In most cases, each port is a standard array of terminals to which any one of a number of peripheral devices--e.g., printers, card readers, disk drives, optical character readers, video display terminals, and modems or other devices for communicating with other computers--can be connected. Many of these peripheral devices are optional, and their absence will not affect the operation of the computer. In fact, large computers are generally provided with large numbers of input/output ports and many remain unused.
Of these ports, some may be dedicated to particular essential peripheral devices. If one of these devices is absent, it may be desirable for the computer to shut down automatically, or to automatically start or stop selected functions. Even if a port is not dedicated, it may be desirable to have some means for informing the central processing unit that it need not search for any input/output devices at that port. At the very least, it is desirable to cover unused ports to keep out dust, and to prevent accidental short circuits or physical terminal damage.
Simple covers which prevent short circuits and physical damage are well known. It is also known to provide terminator devices which indicate to the central processing unit that a port is unused or that is should shut down some or all functions or start some functions. Known terminator devices include a circuit board having impedance elements. The impedance elements are arranged to provide the appropriate information to the central processing unit, whether by matching the characteristic impedance of the input/output port or by presenting some other preselected impedance or impedances to the port or to selected terminals in the port.
The impedance elements on the circuit board must be connected to terminals which can be mated with those of the input/output port. In known terminator devices, the connections are made by providing a plurality of socket terminals on the edge of the circuit board. The terminals are designed to receive straight pins parallel to the surface of the board on which the impedance elements are located. Because many computer input/output ports are not composed of straight pins in the same configuration, it is necessary to interpose an adapter of which one end plugs into the terminals on the edge of the circuit board and which presents on its other end a set of terminals which is "plug-compatible" with the computer in question. The adapter can be separate from the terminator, or it could be built into the same housing as the circuit board. Because a circuit board having such terminals plugs into the port edge-on, it protrudes a relatively large distance from the panel in which the port is located. This is so even if no adapter is necessary. In this position, it could present a hazard to those passing by, and it is susceptible to being damaged or knocked off if struck, because of the relatively larger torque that can be applied. It would be desirable to have terminators protrude as little as possible from the computer panel.
In addition, because of the positioning of the circuit board, the lines on the circuit board are relatively long. It would be desirable to shorten them to reduce signal delay time and power dissipation.